The invention relates to improvements in an external fixation system for stabilizing fractured bones in a living body, component parts of such a system, and methods of facilitating bone healing utilizing such assemblies. There are a wide variety of external fixation systems on the market today, which systems are very useful in facilitating the healing of fractured bones. Such systems are most commonly employed where there is soft tissue loss in order to avoid infection, or where there is the necessity of repairing damaged blood vessels, or if it is necessary to retain joint mobility either above or below the fracture. Typical of successful prior art external fixation systems is one manufactured by ETS Jaquet Freres of Switzerland and distributed in the United States by Howmedica, Inc. of Rutherford, N.J.
While prior systems of external fixation are successful, under some circumstances there can be several drawbacks associated therewith. For instance under some circumstances the healing time for the fracture is unacceptably long, even to the extent that after initial stages of healing the external fixation system is removed and a cast is substituted. Such long healing times may result from inadequate compression applied to the fracture site. It is known that healing is facilitated when appropriate compression is applied to the fracture site, and when after initial healing intermittent axial loads are applied to the fracture site. Because prior external fixation systems perform their stabilizing functions so well, however, it has heretofore been difficult to develop a mechanism or method allowing compression and axial loading of the fracture site to facilitate healing.
According to the apparatus and method of the present invention, an external fixation assembly, and components parts therefor, are provided which provide the simultaneous application of axial loading and compression, facilitating healing so that long healing times associated with external fixation systems in some circumstances may be overcome. Also according to the present invention methods of facilitating fractured bone healing are provided which facilitate sliding of the external fixation frame components to allow, upon loosening of universal joint components of the frame, intermittent axial loads to be applied to the fracture site.
In its simplest terms, the apparatus according to the invention comprises the conventional frame components of universal joints, articulating couplings, and connecting rods with the addition of spring means for applying compressive forces directly to the universal joints. Adjustment of the compressive forces is easily effected utilizing knobs or the like readily accessible on the frame, and the amount of compression provided by the spring means may be positively controlled. Means may be provided for positively preventing distraction, if desired, or distraction can be opposed by the same spring compressive forces that provide the compression.
According to a basic method of the present invention, a fractured bone in a living body is stabilized by inserting pins into bone portions so that end portions of the pins extend externally of the body, and operatively attaching the universal joints, articulation couplings, and rods to the pins to provide the necessary frame for stabilizing the fracture. The method steps are practiced so that upon loosening of the universal joints coupled longitudinal, anterior-posterior, medial-lateral and torsional motion or force applications are provided, free sliding of the universal joints relative to each other also being provided so as to control static or dynamic loading of the fracture site and thereby minimize shear forces and maximize forces normal to the fracture plane.
According to another aspect of the method of the invention, a frame which extends externally of the body is operatively attached to bone portions of the fracture to stabilize the positions of the bone portions in a relative position where proper healing will take place. Predetermined, controlled compressive forces are applied with the frame to the fracture site to facilitate healing, and the frame--with internal compressive forces--is maintained in rigid position stabilizing the fracture and preventing substantially all relative movement between the bone portions until initial healing of the fracture takes place. The initial healing of the fracture must be sufficient to render the fracture capable of accepting intermittent axial loadings. Then the frame may be loosened sufficiently to allow intermittent axial loading of the fracture site while preventing destructive relative movements between the bone portions, and intermittent axial loads are applied to the fracture site to facilitate healing. When healing is substantially completed the frame is then removed. Displacement control of the frame is practiced to control the maximum amount of bone movement in response to intermittent axial loading.
It is the primary object of the present invention to provide improved apparatus and methods for facilitating healing of a fractured bone in a living body. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.